The semilunar valves open when the pressure in the ventricles excedes the diastolic pressure in the artery the ventricle empties into. For example if the diastolic pressure in the aorta is 80 mmHg then the aortic similunar valve will open when the pressure inside the left ventricle surpasses 80 mmHg.
As the ventricles contract, the pressure inside of them increases dramatically. When this pressure becomes higher then the pressure inside the great vessels, the blood literally "pushes" the semilunar valves open and empties into the lower pressure vessels. When they reach equal pressure, the semilunar valves close from blood trying to flow back into the ventricles.
When ventricular pressure exceeds that of the large arteries leaving the heart, the semilunar valves are forced open. (Marieb/9th edition)
Higher pressure on the convex side (from the heart contracting) than the concave side causes them to open. When the pressure reverses (the heart relaxes) they close.
The pulmonic valve opens when the pressure in the right ventricle rises higher than the pressure in the pulmonary artery. It closes when the pressure falls.
The pressure of the blood itself opens the valves.
Semilunar valves are open when the blood is being pumped. The AV valves are closed when the semilunar valves are open.
The semilunar valves are open when blood is being pumped by ventricular contraction. This event is called systole.
Semilunar valves are located at the base of both the pulmonary trunk (pulmonary artery) and the aorta
When ventricular pressure exceeds that of the large arteries leaving the heart, the semilunar valves are forced open. (Marieb/9th edition)
ventricles are in diastole
When ventricular pressure exceeds that of the large arteries leaving the heart, the semilunar valves are forced open. (Marieb/9th edition)
semilunar valves are called semilunar because they look like half a moon. If something is not full in biology it is called 'semi' and lunar means the moon. So basicaly its called that because the valve looks like a half moon.
the function of the semilunar valves are that they provied the lungs with glucose and oxygen
When the ventricular pressure exceeds the pressure in the aorta and pulmonary trunk, the semilunar valves are forced open and blood is ejected out. This signals the ejection phase of the cardiac cycle of ventricular systole.
The tricuspid valves are different from the semilunar valves. The tricuspid valve is the right atrioventricular valve.
Because there are crescent shaped, like half moons :)
The atrioventricular valves prevent the backflow of blood into the atria when the ventricles are contracting. The semilunar valves prevent backflow from the arteries into the ventricles.